In the present work the identical location transmission electron microscopy (IL-TEM) approach is used for a comparative study of the degradation of several standard Pt-based electrocatalysts for low temperature proton conducting membrane fuel cells (PEMFCs). The paper discusses the mechanisms responsible for the Pt surface area loss of carbon supported electrocatalysts. It is demonstrated that seemingly similar catalysts can exhibit under identical treatment pronounced differences in their degradation behaviour. As a consequence individual steps in the synthesis of electrocatalysts can have a distinct effect on the degradation mechanism even if the base chemicals and materials used in their synthesis are identical. This finding sheds new light in the much debated issue if crystallite migration and coalescence or Pt dissolution and re-deposition are mainly responsible for the Pt surface area loss.